As others have said, people prefer different ways. My wife (Japanese) writes on Windows (Japanese edition) in romaji, and she's very fast. But she also says that in fact most Japanese (at least of her generation) don't write that way (they presumably use those small kana letters on Japanese-variant keyboards). As a non-native I also write the way she does, though I'm on Linux. I'm not sure why my wife writes using romaji, I should ask.. she wasn't an English speaker or anything, so why that worked for her I don't know.